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A total of 133 species of birds have been observed in the park and preserve over the past 25 to 30 years. Nearly half of those recorded are normally associated with aquatic habitats.

Raptors inhabiting the park include species of eagles, hawks, falcons, and owls, three jaegers, and the northern shrike. Because of their place high in the food chain, raptors are more susceptible to environmental disturbance and population fluctuations. Arctic peregrine falcons, a threatened species recently removed from the endangered list, nest in the area.

The wildlife of Gates of the Arctic National Park and Preserve is representative of northern Alaska and the Brooks Range. Species are relatively few, and their populations are frequently low compared to numbers in more temperate regions. The populations of some animals such as lynx and hare are characterized by ups and downs called cycles. These may be annual or spread over several years. There are no known threatened or endangered wildlife species within the park and preserve.

A total of 36 species of mammals occur within the park, ranging in size from voles and lemmings to brown bears and moose. Small mammals form the base of the arctic food chain and are a critical element in the survival of many raptors and large mammals. Singing, tundra, and red-backed voles and brown and collared lemmings convert plant resources to flesh on which a variety of predators depend. Collectively, small rodents may have a profound localized effect on tundra vegetation. Larger rodents include the arctic ground squirrel and Alaskan marmot. Arctic ground squirrels occur primarily on well-drained soils along rivers or on slopes. They are commonly observed and can often be a problem at cabins, food caches, and camps.

The furbearers common to Alaska are present: wolverine, marten, lynx, beaver, mink, otter, red foxes, and the occasional arctic fox.

Wolves occur throughout the park and preserve, traveling in packs or family groups as they hunt. The main prey of wolves in the central Brooks Range and on the arctic slope is caribou; however, other prey species may be used extensively if caribou are not available, principally Dall sheep, small mammals, moose, snowshoe hare, and beaver.

Brown bears (barren-ground grizzlies) occur throughout the park and preserve. They are among the earth's largest predators, but in the Brooks Range they feed mostly as vegetarians, eating berries, sedges, hedysarum, and other plants. They also feed on small mammals and may spend hours excavating ground squirrel burrows, locally disrupting much of the ground surface in the pursuit of their prey. The bears will kill moose calves and caribou fawns and occasionally adults. Some scavenging also occurs. Brown bear populations concentrate along most of the major streams and rivers within the park. Although brown bears range through all habitat types, they are most commonly found in open alpine or tundra habitats. Brown bears gain weight rapidly during the late summer and fall and are waddling in fat just prior to denning. At this time most mature males weigh between 500 and 900 pounds with extremely large individuals weighing as much as 1,400 pounds. Females weigh one half to three quarters as much. There is an average of one brown bear for each 100 square miles of habitat in the Arctic.

Black bears, which are more common in the southern forested regions, have similar food habitats and behavior. Black bears are creatures of opportunity when it comes to matters of food. Upon emergence from hibernation in the spring, freshly sprouted green vegetation is the main food item, but blacks will readily take anything they encounter. Things such as winterkilled animals are readily eaten, but carrion is apparently taken only if little else is available. As summer progresses, feeding shifts to salmon if they are available. In areas without salmon, bears rely primarily on vegetation throughout the year. Berries, especially blueberries, are an important late summer and fall food item. Bears are cannibalistic on occasion. An "average" adult male in summer weighs about 180-200 pounds. Black bears have very poor eyesight but their senses of smell and hearing are well-developed.

Moose, Dall sheep, and caribou are the three ungulate mammals occurring in the area. Moose are most common in the forested regions south of the Brooks Range, but their range extends up mountain valleys into the larger northern drainages wherever trees and shrubs provide food and winter habitat. In summer moose frequently move into alpine habitat, but they are uncommon at the crest of the range.

Caribou of the western arctic herd today range over the entire region. The herd declined from a population of at least 242,000 animals in 1970 to an estimated 75,000 animals in 1976. Since that time the herd has increased in size, and in 1982 it was estimated at 171,699 animals. Some of the animals use summer range along the northern reaches of the park, and some winter in the southern part of the park, especially in the Kobuk River valley.

Published: 29 Apr 2002 | Last Updated: 15 Sep 2010 Details mentioned in this article were accurate at the time of publication